The present invention relates to a geared rotary actuator.
Geared rotary actuators are used in, for example, aerospace applications where they may be used in driving aircraft control surfaces, bay doors and the like.
The present invention seeks to provide an improved actuator.
Accordingly, the present invention provides a geared rotary actuator having:
a differential gear unit having a drive input and first and second outputs;
an output driven member for connection to an external member to be driven by the actuator;
and first and second drive paths coupling said first and second outputs of the differential gear unit to said output driven member;
wherein:
the arrangement is such that under normal conditions drive is transmitted from the input drive to the output driven member via the differential unit and the first drive path;
in response to jamming or binding of said first drive path drive is transmitted to said output driven member by way of said differential unit and said second drive path;
and in response to jamming or binding of said differential unit drive is transmitted to said output member via said differential unit and both said first and second drive paths;
the arrangement being further such that the gear ratio between said drive input and said output driven member remains substantially the same.
In a preferred form of the invention the second drive path has an output carrier member which carries the whole of the first drive path such that in response to jamming of said first path the whole of the primary path is caused to rotate on block thereby to transmit drive to the output driven member.
Advantageously, each of the first and second drive paths include a balanced planetary configuration to reduce the tendency of the planets to skew under applied loading.